1. Field of the Invention
The invention relates to a fastener, more particularly to a fastener for a heat-dissipating device.
2. Description of the Related Art
In order to effectively dissipate heat generated by a heat-generating component, such as a central processing unit (CPU) of a computer, generally, a heat sink is caused to abut tightly against a surface of the heat-generating component to help dissipate the heat of the heat-generating component so as to ensure that the heat-generating component can operate under a suitable temperature. In order to enable the heat sink to abut tightly against the surface of the heat-generating component, a securing seat is generally mounted on a circuit board, and a fastener is coupled to the securing seat to apply pressure to the heat sink such that the heat sink abuts tightly against the surface of the heat-generating component.
As shown in FIGS. 1, 2 and 3, a heat sink 10 of a conventional heat-dissipating device is firmly secured on a securing seat 12 by means of two fasteners 11 disposed on two opposite sides of the heat sink 10. Each fastener 11 includes a fastening arm 111 and a fastening member 112 mounted on the fastening arm 111. The fastening arm 111 has an engaging end 113 extending through a securing hole 114 in the fastening member 112. When it is desired to assemble the heat sink 10 to the securing seat 12, an engaging hook 115 of the fastening arm 111 of the fastener 11 is caused to be retained in a positioning hole 121 in the securing seat 12, with the fastening arm 111 abutting against a bottom plate 101 of the heat sink 10. Subsequently, the fastening member 112 is pressed downwardly in a direction indicated by the arrow in FIG. 2 such that an engaging hook 116 at a bottom end thereof is retained in another positioning hole 121 in the securing seat 12, thereby mounting the fastener 11 on the securing seat 12. Thereafter, by repeating the above steps to assemble another fastener 11, two fastening arms 111 of the two fasteners 11 are able to force the heat sink 10 tightly against a surface of a CPU (not shown) . However, since such a downward pressing type fastener 11 does not have a force-saving mechanism, the engaging hook 116 of the fastening member 112 cannot be easily retained in the positioning hole 121, due to an insufficiently applied force, an excessively applied force, or an unevenly applied force exerted by the user during assembly. In addition, if it is desired to remove the fastener 11, a greater downward pressing force is required to be exerted for disengaging the engaging hook 116 from the positioning hole 121. Thus, the fastener 11 is not convenient in terms of removal.
There is proposed another type of fastener for a heat-dissipating device which has a force-saving mechanism, such as the rotary type fastener disclosed in R.O.C. Utility Model Patent No. M287962. In said patent, when it is desired to mount a heat sink on a securing seat, a fastening hole in a coupling end portion of a fastening arm and a fastening hole in a fastening plate are caused to respectively engage two retaining blocks disposed on two opposite sides of the securing seat. Thereafter, by manipulating a protruding block on a switch member to cause the latter to rotate, a shaft is released from a position of engagement in two lower positioning grooves, and is guided by guiding oblique faces to displace upwardly. When the shaft engages two upper positioning grooves, the fastening arm of the fastener can urge the heat sink to abut tightly against a surface of a CPU. Although such a rotary type fastener is relatively convenient and force-saving in terms of detachment of the fastener, the components of the fastener are relatively large in number and are complicated in structure, thereby resulting in a relatively high manufacturing cost.
Referring to FIGS. 4, 5 and 6, in a rotary type fastener 21, a fastening member 212 and an operating member 213 are mounted on a fastening arm 211. The fastening member 212 has two plates 215 that are spaced apart from each other and that extend through two through holes 214 in the fastening arm 211. The operating member 213 is pivoted between the two plates 215 by means of a rivet 216. When it is desired to assemble a heat sink 20 to a securing seat 22, a fastening hole 217 in one end of the fastening arm 211 and a fastening hole 218 in a bottom end of one of the plates 215 of the fastening member 212 are caused to respectively engage two retaining blocks 221 disposed on two opposite sides of the securing seat 22, followed by turning of the operating member 213 in a direction indicated by the arrow in FIG. 5. With a curved face 219 of the operating member 213 pushing the fastening arm 211 to displace downwardly and with the operating member 213 bringing the fastening member 212 to displace upwardly, the retaining blocks 221 can firmly engage the fastening holes 217, 218, and the fastening arm 211 can force the heat sink 20 against a surface of a CPU (not shown). Since both the fastening arm 211 and the operating member 213 of the fastener 21 are formed from a metal material, and since the operating member 213 of the fastener 21 will rub against the fastening arm 211 during the turning process, metal shavings (not shown) are generated. If the metal shavings fall onto a circuit board (not shown), short-circuiting or malfunctioning of the circuit board is likely to result.